The invention relates to improvements in hinge joints of hinge fittings in general, and more particularly to improvements in hinge joints which can be utilized with advantage on seats of motor vehicles, especially to permit adjustments of inclination of the back relative to the weight carrying part of a seat. Still more particularly, the invention relates to improvements in hinge joints of the type wherein the inclination of a pivotable component with reference to a second component can be altered by changing the angular position of a shaft, a pintle or an analogous coupling element, either by a manually operated device or by a motor.
Commonly owned U.S. Pat. No. 4,708,392 granted Nov. 24, 1987 to Heinz Werner et al. discloses a hinge joint wherein the shaft is provided with a cylindrical eccentric for one gear of the transmission between the two components and with a frustoconical eccentric surrounded by the internal surface of a supporting member which is affixed to the weight carrying part of the seat. The eccentricity of the frustoconical eccentric exceeds that of the cylindrical eccentric, and the frustoconical eccentric serves to effect an axial movement of the shaft and of the member which engages the frustoconical eccentric relative to each other while the shaft is rotated to effect a radial movement of the aforementioned member, i.e., to eliminate radial play between mating parts of the transmission. The magnitude of radial forces increases in response to rotation of the shaft, and this entails an axial movement of the shaft in order to permit a reduction of the force which is necessary to change the angular position of the shaft. When the adjustment is completed the shaft should remain in the newly selected axial position until but is likely to leave such position as a result of vibration and/or other stray movements when the vehicle is in motion. The extent of axial shifting of the shaft during angular displacement depends on the magnitude of tolerances between mating parts of the transmission. Such axial shifting contributes to complexity of the adjusting mechanism for the seat, especially if each seat is equipped with two hinge joints, one at each of its sides. As a rule, the shaft of one of the hinge joints is connected with the shaft of the other hinge joint by a torque transmitting device in the form of a rod or the like so that a single handwheel or a single motor will suffice to simultaneously turn both shafts when the occupant of the seat desires to change the inclination of the back. The torque transmitting mechanism between the shafts of the two hinge joints must be designed with a view to take into consideration axial movability of the shafts.